Investigating the suitability of dichotomous responses for the Water Insecurity Experiences (WISE) Scales using nationally representative data from 39 countries

The Water Insecurity Experiences (WISE) Scales have been validated to comparably measure water insecurity globally. The scales consist of 12 items that can be administered in approximately 3 minutes. There is interest in developing more rapid versions of the tools for when time is limited. One alternative is to use a subset of 4 items, which has been validated, but has some drawbacks. Here we investigate another alternative: dichotomous (yes/no) response options instead of the original four levels of frequency-based (polytomous) responses. We used nationally representative data from 39 countries to simulate dichotomized responses by collapsing the four levels of frequency (never, rarely, sometimes, often/always) into yes/no. We first explored if “rarely” is meaningful in the gradation of water insecurity, as experiences that occur “rarely” may not be affirmed with dichotomous response options. We tested item-by-item if “rarely” responses predicted dissatisfaction with water quality using logistic regression and found that they were associated with higher odds of dissatisfaction with water quality. As such, some meaningful nuance may be lost if “rare” experiences are not affirmed as “yes”. We then compared the predictive accuracy of WISE scores using simulated dichotomous responses compared to those calculated using polytomous responses. Based on receiver-operator-characteristic (ROC) curves and regression models, scores calculated using dichotomized responses had good predictive accuracy. Scores calculated using the abbreviated 4-item version were similarly accurate. Finally, we examined whether levels of water insecurity, as calculated from the original responses, could be classified using dichotomized responses. Using ROC curves, we found that this approach was effective, offering an advantage over the 4-item scales. While polytomous response options provide more detailed information, dichotomous responses offer the potential advantage of a quicker alternative for measuring water insecurity.